The present invention relates generally to balloon dilatation catheters, and, in particular, to a specially configured balloon for implanting and/or sizing an implantable stent at an ostial treatment site.
In a typical percutaneous transluminal coronary angioplasty (PTCA) procedure, a guiding catheter is percutaneously introduced into the patient's cardiovascular system through the brachial or femoral arteries. The guiding catheter is advanced through the patient's vasculature until the distal end is in or near the ostium of the desired coronary artery. A guidewire is thereafter advanced through the guiding catheter and into the patient's coronary vasculature.
A balloon dilatation catheter is thereafter advanced over or along the guidewire until the dilatation balloon is properly positioned within a treatment site. Following positioning of the dilatation catheter, the balloon is inflated to a predetermined size by infusion of an inflation media at relatively high pressures. The inflated balloon radially enlarges the lumen (passage) at the treatment site by compressing the lesion against the artery wall. The balloon is thereafter deflated to a relatively smaller profile, so that the dilatation catheter can be proximally withdrawn from the patient's vasculature and blood flow resumed through the dilated artery.
Some lesions may benefit from deployment of an intravascular prosthesis (stent) immediately after coronary angioplasty to scaffold a flow-limiting dissection, thus obviating the need for emergency coronary artery bypass surgery. Also, certain de novo (new) lesions and some lesions which have developed restenosis may be associated with lower restenosis rates after stent deployment. That is, the risk of restenosis for certain types of lesions can be improved upon by implanting an intravascular prosthesis to maintain vascular patency within the artery at the site of the lesion.
The stent is generally a radially expandable tubular structure, such as a tubular metal mesh, which can be carried to the treatment site on a deflated deployment balloon. The deployment balloon is appropriately positioned within the vessel and inflated to radially outwardly expand the stent against the vessel wall. The deployment balloon can thereafter be deflated and removed from the patient, leaving a radially enlarged tubular stent in place within the treatment site. A variety of expandable tubular stents suitable for use in the coronary artery are known, for example the Palmaz-Schatz stent available from Johnson & Johnson.
Following stent deployment, a second catheter is sometimes positioned within the stent and expanded to accomplish a final "sizing" of the stent within the artery. A variety of stent deployment balloons and stent sizing balloons are known in the art.
Efforts in the deployment balloon and sizing balloon prior art have generally been directed to ensuring a uniform, generally cylindrical inflated profile in the enlarged balloon, so that the stent will be enlarged to a cylindrical final profile. See, for example, U.S. Pat. No. 5,409,495 to Osborn, disclosing a balloon design which is said to eliminate the "problem" of a dog bone-shaped inflated profile in the expanded stent.
Notwithstanding the various efforts in the prior art, the use of cylindrical stents presents some difficulties for treating lesions in certain relatively common locations. For example, in order to treat lesions at or near an arterial branch point, such as the ostium of the right coronary artery, the stent must either project into the aorta or risk not fully covering the proximal portion of the lesion. There remains a need, therefore, for a specialized balloon, designed to inflate or size a previously inflated stent to a specialized inflated profile to treat certain coronary vascular treatment sites.